A movement guiding device provided with rolling elements, such as balls or rollers, and arranged in guiding parts of a moving object moving linearly have now been used so that the device is able to perform a guide function using rolling movements of the rolling elements. In late years, this kind of movement guiding device has many applications in a clean environment, which is required by, for example, apparatuses for manufacturing semiconductors and liquid crystal products, and medical facilities. With semiconductors highly integrated and other factors, it has now been indispensable that semiconductor manufacturing lines be processed in a vacuum atmosphere.
When a general type of grease is applied in a vacuum environment, the grease is subjected to vaporization of its oil component so that lubricating property will be lost in the grease. Therefore, even if a movement guiding device is used under normal use conditions without any problem, the movement guiding device will encounter various problems when being used in the vacuum environment. The problems include not only an early disappearance of lubricating property of the grease applied inside the device but also discharging a vaporized gas from the grease, resulting in a fear that the outside environment is polluted.
In consideration of these problems, as a lubricant applied in movement guiding devices used in the vacuum environment, a vacuum grease is used which contains an inert fluorinated oil as its base oil. This vacuum grease is lower in general in steam pressure than a grease which contains a mineral oil to be used in the atmosphere. However, for applications in higher vacuum environments, use of the vacuum grease inevitably results in the vaporization of the oil component. Hence it is obliged to use a solid lubricant.